(a) Field of the Invention
The present invention relates to a control system for an LEO (low-earth orbit) satellite. More specifically, the present invention relates to an LEO satellite command planning device and method thereof, and an LEO satellite control system including the same for an LEO satellite control system to plan mission commands so that a satellite may execute missions according to a mission schedule that is a mission plan result.
(b) Description of the Related Art
Satellite missions are planned by a ground control system according to requests by a satellite user. In the mission planning, it is required to appropriately arrange the satellite missions without clash of the missions, and results obtained from the appropriate arrangement is a mission schedule.
To operate the satellite according to the above-planned mission schedule, it is needed for the ground control system to transmit satellite commands recognizable by the satellite to the satellite. In this instance, tasks of generating from the satellite task schedule the tasks that will be transmitted to the satellite are referred to as a satellite command plan Also, satellite commands resulting from the satellite task schedule are converted to radio wave signals and transferred to the satellite when the LEO satellite passes over the control station.
Meanwhile, since the satellite commands for executing predetermined satellite tasks do not include a single telecommand but rather they comprise a set of commands for sequentially operating various devices in the satellite, it is impossible to map a single task into a single satellite command. Also, the identical satellite task can be configured as a different set of satellite commands depending on related parameters. For example, regarding a task of photographing earth images, configurations of a set of sequentially executed task commands are differentiated according to the states of with what degrees of a roll angle the satellite are to shoot the earth images.
The satellite commands are classified as real time commands, absolute time commands, and relative time commands according to execution time. The relative time commands are defined to execute commands after previous commands have been executed and a predetermined time has passed. In general, the satellite commands that are to be sequentially executed are included in the set of satellite commands, which are referred to as a relative time command sequence. Actually, the satellite commands mingled with the previously-noted real time commands, absolute time commands, and relative time commands in a complex manner are transferred to the satellite.
In the conventional satellite control system, an operator can define a single set of satellite commands allocated to a predetermined satellite task. However, the operator cannot select an inner configuration of the set of satellite commands that are to be differentiated according to the parameters related to the satellite tasks in the satellite control system, it is required for a satellite operator to manually select the configuration of the set of satellite commands following the corresponding parameters and input the same as data. If a wrong set of satellite commands is transferred to the satellite because of mistakes of the operator, the satellite malfunctions and enters into a safe hold mode. It then requires a lot of time and effort to switch the satellite to the normal mode, and the satellite cannot execute the tasks while switching to the normal mode.